adding additional command attachment unused, which lists or removes unused attachments; when calling attachment unused list the output could be piped and afterwards opened by OpenOffice Calc by using separator ":"

Refs #9789: Renamed 0.11 directory to trunk. Deleted the 0.12 directory. Diff of the two branches showed that they were identical. Maintaining a single codeline that works for Trac 0.11 and greater will ease maintenance. Added a tags which will be utilized in future releases.